Precise measurement of inner diameter of mono-capillary optic using X-ray imaging technique.

BACKGROUND: Mono-capillary optics have been applied to increase the performance of X-ray instruments. However, performance of a mono-capillary optic strongly depends on the shape accuracy, which is determined by the diameters of the inner hollow of the capillary along the axial direction. OBJECTIVE: To precisely determine the inner diameter of the capillary optic used in X-ray imaging technique, which aims to replace the conventional method using a visible microscope. METHODS: High spatial resolution X-ray images of the mono-capillary optic were obtained by a synchrotron radiation beamline. The inner diameter of the mono-capillary optic was measured and analyzed by the pixel values of the X-ray image. RESULT: Edge enhancement effect was quite useful in determining the inner diameter, and the accuracy of the diameter determination was less than 1.32 µm. Many images obtained by scanning the mono-capillary optic along the axial direction were combined, and the axial profile, consisting of diameters along the axial direction, was obtained from the combined image. The X-ray imaging method could provide an accurate measurement with slope error of±19 µrad. CONCLUSIONS: Applying X-ray imaging technique to determine the inner diameter of a mono-capillary optic can contribute to increasing fabrication accuracy of the mono-capillary optic through a feedback process between the fabrication and measurement of its diameter.

Monochromatic x-rays for low-dose digital mammography: preliminary results.

PURPOSE: The feasibility of using monochromatic x-ray imaging generated from an x-ray tube and a multilayer reflector for digital mammography with a low radiation dose was examined. MATERIALS AND METHODS: A multilayer mirror was designed to select the x-ray peak with an energy of 21.5 keV generated from an x-ray tube with a tungsten target and was fabricated by the ion-beam sputtering deposition system. Monochromatic x-ray images were obtained from an experimental digital mammography setup with a scanning stage. The performance of the system was evaluated using a breast phantom, a spectrometer, and a radiation dosimeter. We measured the contrast-to-noise ratio and performed the 10% modulation function test to determine image quality and resolution. RESULTS: The monochromatic beam from the multilayer reflector had a full-width-at-half-maximum of 0.9 keV at 21.5 keV, and the reflectivity was 0.70, which was 90% of the designed value. The polychromatic and monochromatic x-rays showed radiation doses of 0.497 and 0.0415 mGy, respectively. The monochromatic x-ray image shows fibers, calcifications, and masses more clearly than the polychromatic x-ray images do. The image contrast of the monochromatic x-rays was 1.85 times higher than that of the polychromatic x-rays. The experimental mammography setup had a spatial resolution of 7 lp/mm with both x-rays. CONCLUSION: Monochromatic x-rays generated using a multilayer mirror may be a useful diagnostic tool for breast examination by providing high contrast imaging with a low radiation dose.

Usefulness of a small-field digital mammographic imaging system using parabolic polycapillary optics as a diagnostic imaging tool: a preliminary study.

OBJECTIVE: To evaluate the efficacy for spatial resolution and radiation dose of a small-field digital mammographic imaging system using parabolic polycapillary optics. MATERIALS AND METHODS: We developed a small-field digital mammographic imaging system composed of a CCD (charge coupled device) detector and an X-ray source coupled with parabolic polycapillary optics. The spatial resolution and radiation dose according to various filters were evaluated for a small-field digital mammographic imaging system. The images of a test standard phantom and breast cancer tissue sample were obtained. RESULTS: The small-field digital mammographic imaging system had spatial resolutions of 12 lp/mm with molybdenum and rhodium filters with a 25-microm thickness. With a thicker molybdenum filter (100 microm thick), the system had a higher spatial resolution of 11 lp/mm and contrast of 0.48. The radiation dose for a rhodium filter with a 25-microm thickness was 0.13 mGy within a 10-mm-diameter local field. A larger field image greater than 10 mm in diameter could be obtained by scanning an object. On the small-field mammographic imaging system, microcalcifications of breast cancer tissue were clearly observed. CONCLUSION: A small-field digital mammographic imaging system with parabolic polycapillary optics may be a useful diagnostic tool for providing high-resolution imaging with a low radiation dose for examination of local volumes of breast tissue.

Micro-CT imaging with a hepatocyte-selective contrast agent for detecting liver metastasis in living mice.

RATIONALE AND OBJECTIVES: Micro-computed tomography (CT) is a important tool for longitudinal imaging of tumor development. The detection and monitoring of tumors in the liver in live animals using micro-CT is challenging. We evaluated the feasibility of high-resolution micro-CT enhanced with a hepatocyte-selective contrast agent for detecting liver metastases in a live murine model. MATERIALS AND METHODS: Hepatic metastases were induced in 10 BALB/C mice. Two mice each were randomly selected on days 3, 5, 7, 10, and 13 after CT26 colon adenocarcinoma cells were injected into the portal vein; micro-CT imaging was performed at 10 minutes and 4 hours after intravenous administration of a hepatocyte-selective contrast agent at a dose of 0.4 mL/mouse. The attenuation values of the normal liver and the tumors were obtained. The number of metastases was counted and their sizes were measured on the micro-CT images. Gross or histopathologic evaluation was performed for correlating the liver tumors with the micro-CT images. RESULTS: A total of 74 separate tumor sites larger than 300 microm in diameter were detected on pathologic examination of the mice that were sacrificed 7 days after cell injection. On micro-CT, 66 of 74 tumors were detected (83.8%). The smallest tumor detected on micro-CT was 300 microm. There were eight false-negative readings on micro-CT. The sizes of the individual liver metastases measured by micro-CT and on the excised specimen were highly correlated (P < .001). The correlation between the CT scan measurement and the actual measurement was r = 0.8354 (P < .0001). CONCLUSIONS: High-resolution micro-CT enhanced with a hepatocyte-selective contrast agent can be a promising tool for detecting liver metastases in a live murine model.

Figure tolerance of a Wolter type I mirror for a soft-x-ray microscope.

The demand for an x-ray microscope has received much attention because of the desire to study living cells at a high resolution and in a hydrated environment. A Wolter type I mirror used for soft-x-ray microscope optics has many advantages. From the mirror fabrication point of view, it is necessary to perform tolerance analysis, particularly with respect to figure errors that considerably degrade the image quality. The figure tolerance of a Wolter type I mirror for a biological application in terms of the image quality and the state-of-the-art fabrication technology is discussed. The figure errors rapidly destroyed the image quality, and the required slope error depended on the detector used in the soft-x-ray microscope.

Wolter type I x-ray focusing mirror using multilayer coatings.

A multilayer coating is a useful addition to a mirror in the x-ray region and has been applied to normal incidence mirrors used with soft x rays. When a multilayer coating is used on grazing incidence optics, higher performance can be achieved than without it. Cr/Sc multilayers coated on a Wolter type I mirror substrate for a soft x-ray microscope are considered. The reflectivity and effective solid angle are calculated for Wolter type I mirrors with uniform and laterally graded multilayer coatings. The laterally graded multilayer mirror showed superior x-ray performance, and the multilayer tolerances were relaxed. This multilayer mirror could be especially useful in the soft x-ray microscope intended for biological applications.

Compact soft x-ray transmission microscopy with sub-50 nm spatial resolution.

In this paper, the development of compact transmission soft x-ray microscopy (XM) with sub-50 nm spatial resolution for biomedical applications is described. The compact transmission soft x-ray microscope operates at lambda = 2.88 nm (430 eV) and is based on a tabletop regenerative x-ray source in combination with a tandem ellipsoidal condenser mirror for sample illumination, an objective micro zone plate and a thinned back-illuminated charge coupled device to record an x-ray image. The new, compact x-ray microscope system requires the fabrication of proper x-ray optical devices in order to obtain high-quality images. For an application-oriented microscope, the alignment procedure is fully automated via computer control through a graphic user interface. In imaging studies using our compact XM system, a gold mesh image was obtained with 45 nm resolution at x580 magnification and 1 min exposure. Images of a biological sample (Coscinodiscus oculoides) were recorded.